What would you say about your gym charging you only for days that you fail to actually show up and work out? That’s the premise behind Gym-Pact, a fitness program developed by Harvard University business graduates, that’s expanding across gyms nationwide.

The business model is based on motivational economics, basically incentivizing patrons to keep their New Year’s resolutions. Rather than tossing down cash upfront, and then putting it out of your mind as the months roll by and the rolls pile up each month, Gym-Pact is turning the entire industry standard on it’s head.

Gym-Pact offers what Zhang calls motivational fees — customers agree to pay more if they miss their scheduled workouts, literally buying into a financial penalty if they don’t stick to their fitness plans. The concept arose from Zhang’s behavioral economics class at Harvard, where professor Sendhil Mullainathan taught that people are more motivated by immediate consequences than by future possibilities.

Zhang and Oberhofer translated that principle to workout motivation. If missing a workout cost people money, they’d be more motivated to stick with it, they thought.

“If you have a toothache, you go to the dentist. If there’s a cavity, you know it needs to get filled in, but if it doesn’t hurt right now, you may not bother,’’ Mullainathan said. “In traditional gym memberships, not going is not very costly. In this one, you actually might feel the pain of not going immediately.’’

Participation is completely opt-in, but people are volunteering for the service left and right.

Amanda Deutsch, a student at Harvard, joined Gym-Pact in January because she “thought it’d be a good way to get myself to go to the gym a bit more often.’’

So far, it has worked.

“I can’t imagine that people want to pay,’’ she said.

In order to validate gym-goers attendance, a secret code is refreshed at the front counter of participating gyms every 60 seconds. Patrons text message the code to the Gym-Pact number as they enter and exit the gym on workout days.

We love this idea! The Unicorn Booty team makes it down to the gym each day (Have you seeeeen these abs?), because it feels great, and we spend quite a bit of time sitting on our asses in front of computer screens each day. We love the idea of incentivizing fitness, and we’re looking forward to watching this program expand.

Would you work out more often if you had to pay for not going to the gym?